P Block Elements

Given are \(\mathrm{H}_3 \mathrm{PO}_2, \mathrm{H}_3 \mathrm{PO}_3, \mathrm{H}_3 \mathrm{PO}_4\) and \(\mathrm{H}_4 \mathrm{P}_2 \mathrm{O}_7\). Which of the above oxacids results into two series of salts?